Week 6 – Patience is a Virtue

July 28th, 2016

This week, I learned the importance of running one’s hefty MATLAB scripts over the weekend whenever possible. Rob and I recently made the decision to filter the THOR data using a center frequency range of 1-50 Hz instead of 1-100 Hz. Since my Gaussian band-pass filters require equal relative bandwidths, this involved re-designing my set of 30 filters and subsequently re-filtering the data. This last step is what taught me my lesson. I had over 150 shots to filter. Each contained about 300 to 350 traces. Each trace had to be filtered 30 times. That’s at minimum over 1.3 million operations. To compound everything, I was using filtfilt, MATLAB’s fancy, computationally-intensive zero-phase filter function.

Long story short, my poor Mac mini kept a high temperature most of the week as it churned through trace after trace (unfortunately, no faster machine was available). The whole process ended up taking over 80 hours to complete. While the filter script was chugging along, I began tackling the rather steep learning curve of the Generic Mapping Tools (GMT), a set of command-line tools used to make manuscript-quality plots and maps. After quite a few frustrating hours, I ended up with this GROOVY map of Yucca Flat.

Figure 11: A map of the THOR study area, composed in GMT. White circles indicate shot locations. Check out all those craters!

After scrambling past the steepest part of GMT’s learning curve, I can certainly see the benefits. One can make simple maps with just a few lines of code, and it’s free, which is a godsend considering how expensive licenses for dedicated software packages such as ArcGIS can become. GMT is quite popular with geophysicists for these reasons. Plus, with all the funky option flags and lack of spaces, it makes you feel like a super cool coding expert when you get things right. That’s probably another reason why geophysicists favor it…

I’m eagerly anticipating our upcoming seismic data acquisition campaign at the NNSS. There’s been a seemingly never-ending stream of training and logistics to work through, and I’ve already learned loads about the intricate preparation required for a field experiment taking place at such a secure location. I’m especially looking forward to the change of scenery. After weeks sitting at a computer, spending some time outside performing physical labor will be a welcome change – even if it’s going to be tough.

Outside of the science realm: This Saturday I realized – unbearably late into my internship – that ABQ has its own lift-served bike terrain! There aren’t too many trails to explore, but nevertheless it’s always fun to ride on a chairlift in the summer, especially when it’s in lieu of climbing thousands of feet on your bike at high elevation. A brief hike got me from the top of the lift to the crest of the Sandias, which presented a breathtaking view. The east side of the Sandia crest is fairly gentle (that’s where the ski and biking area is) while the west face, the part visible from the city, is aggressively steep and rugged. The drop-off is nearly nausea-inducing, and the city looks strange, almost too flat, from the high vantage point. I’d love to return at some point and catch the sunset, since I’m convinced it would be absurdly gorgeous from the crest.

Figure 12: After a long day of descending.

Comments

GMT makes excellent maps and it's good to get on the learning curve early. have yet to master it and will probably start walking up that curve myself in the future! There are some nice mapping toolboxes in MATLAB that I use and jive well with my MATLAB codes. However, I do think that GMT products just come out looking a bit more polished.